Vapor deposition surface treatment methods include evaporation, plasma multi-arc sputtering, magnetron sputtering and reactive sputtering. Magnetron sputtering is widely used in the manufacturing industry of automotive parts. Automotive hubs using magnetron sputtering as surface decoration have been applied and promoted in the after-market. The characteristic of magnetron sputtering is to make the surface of a part achieve the metallic mirror gloss decoration effect. By combining with conventional coating, not only is the part attractive, but also the coating performance can meet the automotive factory standards.
Magnetron sputtering is a method that the working gas is ionized in a vacuum chamber, the ionized ions bombard a metal target at a high speed under the mixed field action of an electric field and a magnetic field and the metal atoms or ions on the target sputter out and are deposited on the surface of a workpiece. This method can achieve a new effect of metallic appearance of a glossy mirror, and is environment-friendly and low in cost. The target may be a non-magnetic metal, a non-metal or an alloy. According to the corrosion resistance standard of a main engine plant coating, an appropriate metal or alloy is selected to meet the requirements for surface corrosion resistance, weather resistance, decorativeness and the like. The surface of the aluminum alloy cast hub is relatively rough and cannot be directly coated to form a smooth and bright coating film, so an organic coating must be sprayed onto the hub, and then a metal film is sputtered on the bright organic coating. In order to prolong the long-term gloss of the metal coating film, a transparent powder coating is sprayed onto the coating film, so that the coating film material achieves good binding force with the upper and lower organic coatings. The coating film itself must also have high corrosion resistance.
There are three types of magnetron sputtering methods: I, a black transparent paint is sprayed onto the bright white metal coating film to achieve a bright black chromium appearance; II, black high-gloss resin is sprayed onto the metal coating film to reduce the thickness of the coating film, so that the coating film is translucent, transmits the underlying black and is black and bright; the above two methods have respective advantages and disadvantages: in the first method, the color transparent paint easily produces color aberration, the black transparent paint is different in thickness and color, and the black transparent coating generally has a thickness of 10-30 microns, is poor in protection on the coating film and cannot achieve long-term use standards; and in the second method, the translucent coating film cannot completely cover the underlying resin, and long-term exposure and ultraviolet aging lead to interlayer adhesion failure.